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Job Interviews: What is Normalization?


Job Interviews: What is Normalization?

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Andy Clap
Andy Clap
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Thanks for the linked "tutorial" on database design. Nicely written, I've shared it with a couple of colleagues who are pretty new to this.
http://www.sqlservercentral.com/articles/Database+Design/72054/
Dalkeith
Dalkeith
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As a side note what do people consider the best way of arranging tables for storing family relationships?

My journey was

Stage 1: Flat table (with total ignorance of the fact that a table can be related to itself)
Stage 2 : Junction Tables for children only
Stage 3: Key value relationship with tag for type of relationship
Final Stage : Back to Flat table with two fields for mother and father this time with knowledge that tables can be self referential

My eureka moment was that parent to child relationship can be looked at from the parent or from the child. Yes a parent can infinite children but a child can only have (ignoring messy breakthroughs in science) two parents - so we are dealing with a 1 to 2 relationship where the child is actually the parent record Smile. Put people in an individuals table enforce completion of parents fields and if you have full field completion you can in theory work out all relationships to all individuals with zero data duplication.

Its an interesting thing a one to many relationship is in itself actually a set of all the 1:n relationships and a 1:2 relationship can be considered as just two 1:1 relationships which hey isn't that the definition of a tuple.

Happy days!

SUGAR - need to revise some former systems!
call.copse
call.copse
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Hmm, I have known the formal definitions and not too long ago, I think I know all the elements and I certainly know what to actually do, however I couldn't define the forms without looking them up. Not worth actually doing until an interview as I'd forget it anyway IMO!
RonKyle
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Preppingfor an interview shouldn't be a cram session to learn more, but really a reviewof concepts you understand.


Exactly. At the moment I would have a little trouble keeping the normal forms straight, although I could give lots of examples. Normalization, ACID, transaction isolations are examples of things I review before an interview just to refresh the details.




xsevensinzx
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call.copse - Friday, January 12, 2018 2:40 AM
Hmm, I have known the formal definitions and not too long ago, I think I know all the elements and I certainly know what to actually do, however I couldn't define the forms without looking them up. Not worth actually doing until an interview as I'd forget it anyway IMO!

Similar here. There is a lot of mundane stuff out there you just can't speak to in terms of correct and technical definitions. Doesn't mean you can't do it or understand it.

For example, I played guitar for 10 years, still can't read sheet music. I still don't hold the neck right compared to what a guitar teacher showed me. I still can't name all the notes, but I still play very complex music.

But there are certain things too, like point-in-time recovery. If you're working with a mission critical system, the time your wasting to look it up, some doctor may not be able to access critical information to save a patience life versus the senior DBA who actually knows his stuff is midway through the recovery while you are still on Google reading some SQLServerCentral.com post from 2014 that Jeff Moden made. Crazy

RandomStream
RandomStream
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xsevensinzx - Friday, January 12, 2018 9:52 AM
call.copse - Friday, January 12, 2018 2:40 AM
Hmm, I have known the formal definitions and not too long ago, I think I know all the elements and I certainly know what to actually do, however I couldn't define the forms without looking them up. Not worth actually doing until an interview as I'd forget it anyway IMO!

Similar here. There is a lot of mundane stuff out there you just can't speak to in terms of correct and technical definitions. Doesn't mean you can't do it or understand it.

For example, I played guitar for 10 years, still can't read sheet music. I still don't hold the neck right compared to what a guitar teacher showed me. I still can't name all the notes, but I still play very complex music.

But there are certain things too, like point-in-time recovery. If you're working with a mission critical system, the time your wasting to look it up, some doctor may not be able to access critical information to save a patience life versus the senior DBA who actually knows his stuff is midway through the recovery while you are still on Google reading some SQLServerCentral.com post from 2014 that Jeff Moden made. Crazy

Actually I've only read up to Jeff's 2011 but I get your point.
I'd explain it to the interviewer like we were both 5:
When you are dating someone in hot demand, you have to be around her all the time, like putting you name all over her to keep away jerks in the bar.
Then you get married - the relationship established. You no longer need to be around 24x7. In fact you may crave a bit of alone time. That's what we call Normalization. So tell me again please the part about 4-week paid vacation in the compensation package...

JaybeeSQL
JaybeeSQL
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RandomStream - Friday, January 12, 2018 5:24 PM
xsevensinzx - Friday, January 12, 2018 9:52 AM
call.copse - Friday, January 12, 2018 2:40 AM
Hmm, I have known the formal definitions and not too long ago, I think I know all the elements and I certainly know what to actually do, however I couldn't define the forms without looking them up. Not worth actually doing until an interview as I'd forget it anyway IMO!

Similar here. There is a lot of mundane stuff out there you just can't speak to in terms of correct and technical definitions. Doesn't mean you can't do it or understand it.

For example, I played guitar for 10 years, still can't read sheet music. I still don't hold the neck right compared to what a guitar teacher showed me. I still can't name all the notes, but I still play very complex music.

But there are certain things too, like point-in-time recovery. If you're working with a mission critical system, the time your wasting to look it up, some doctor may not be able to access critical information to save a patience life versus the senior DBA who actually knows his stuff is midway through the recovery while you are still on Google reading some SQLServerCentral.com post from 2014 that Jeff Moden made. Crazy

Actually I've only read up to Jeff's 2011 but I get your point.
I'd explain it to the interviewer like we were both 5:
When you are dating someone in hot demand, you have to be around her all the time, like putting you name all over her to keep away jerks in the bar.
Then you get married - the relationship established. You no longer need to be around 24x7. In fact you may crave a bit of alone time. That's what we call Normalization. So tell me again please the part about 4-week paid vacation in the compensation package...


If you were to malign red-blooded men who are simply acting upon our most natural of instincts as 'jerks' at interview, well I hope your tech skills are top-notch, if not you can expect a 'No thanks' email via the recruiter from me.
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